This invention relates to the field of computer input devices, and more particularly to pointing devices and fingerprint acquisition devices.
Fingerprint matching is a well-established and reliable method of identifying individuals. As such, it provides a good method for authentication of the identity of a person for such purposes as enabling use of equipment, access to data, and the authorization of transactions. In recent years, powerful processors and new algorithms, coupled with a variety of new, xe2x80x9clivescanxe2x80x9d fingerprint scanning devices, have enabled the automatic verification of fingerprints on small computer platforms.
The incorporation of such authentication devices would be particularly useful for notebook, laptop and other portable, mobile computers. Mobile computers are more likely than desktop computers to be present in unsecured areas where unauthorized individuals might attempt to use or access the computer. Because users of such mobile computers often have confidential or proprietary information stored in these computers, such users have a strong interest in maintaining the security of their computers.
Nevertheless, prior security systems for such computers require intentional, active intervention by the user, such as entering passwords or using keylocks. The inconvenience of such frequent activity, in conjunction with the user""s fears of misplacing or forgetting the key or password, often result in users ignoring available security systems.
At the same time, most common computer operating systems presently incorporate windowing in presenting information to users. Common examples of such software, often referred to as graphical user interfaces (GUIs), include Microsoft Corporation""s Windows series and Apple Corporation""s Mac OS. In such computer systems, a spatial metaphor is used to present information.
Some kind of pointing device is almost indispensable for the use of such a computer interface. Beginning with the mouse, a wide variety of pointing devices have been introduced, including trackballs, touchpads, and a variety of mechanical pointers. An example of such a pointing device is described in U.S. Pat. No. 5,489,900 by Cali et al, xe2x80x9cForce Sensitive Transducer for Use in a Computer Keyboard.xe2x80x9d
Such pointing devices which are alternative to the mouse are especially desirable for use with mobile computers. The users of such mobile computers often do not have available the large, flat space necessary for operating the traditional mouse.
Hence, a flood of pointing devices has been introduced in recent years, adapted for use with mobile computers. Each such device has advantages and disadvantages, allowing for a range of alternatives which may be adapted to a variety of usage scenarios and personal preferences.
It would therefore be desirable to provide a fingerprint authentication device capable of allowing user pointing, one which is compact enough for incorporation into a mobile computer. Such a device would allow for user authentication without separate, active intervention by the user.
It is therefore an object of the present invention to provide a combined fingerprint scanner and pointing device. Such a device has the natural advantages of requiring less volume, mass and external surface area than two separate devices, and would cost less and be simpler to incorporate into space restricted systems, such as mobile computers.
Hence, a system is provided according to the present invention for imaging a fingerprint for input of pointing information for a computer. The system includes a fingerprint image acquisition scanner for acquiring a fingerprint image of a finger. The system also includes an image processor for extracting from the fingerprint image at least one contact parameter in addition to authentication status data for the fingerprint image. Such contact parameters may include the two dimensional spatial location of the fingerprint on the scanner, as well as estimates for the force applied by the finger or the rotational orientation of the finger.
In addition to providing the capabilities of a simple pointing device and an ordinary fingerprint scanner, the combination of the two functions into a single system has a number of useful advantages not seen in either single-purpose device. Incorporating the pointing device functionality allows the fingerprint to be passively acquired, without requiring repeated explicit authentication which could take time and interrupt work flow. Thus, the system according to the present invention can operate as a continuously functioning xe2x80x98dead handxe2x80x99 authentication device.
The system, or the attached computer, could maintain a flag which contains data indicating the present authentication. The flag can be made to expire under a variety of conditions, including upon powering down the computer, after passage of a predefined time interval, if a predetermined high value transaction is initiated, etc. On expiration of the flag, the user could be prompted to present a finger for imaging. However, during normal usage of the system, the image obtained during normal pointing or other data input operations could be used for authentication and used to reset the authentication flag.
As a pointing device, the only output required is usually only a simple two dimensional (x,y) coordinate. Such a coordinate can be calculated in a variety of ways. The system according to the presently preferred embodiment calculates the center of area of all of the xe2x80x9conxe2x80x9d-pixels of the acquired fingerprint image. The computed coordinates could be used directly in a computer interface as an absolute coordinate, in a manner similar to a computer tablet. In the alternative, the coordinates could be computed such that changes over time could be calculated and integrated, in a manner similar to that commonly used with a mouse.
Furthermore, other information can be extracted from the fingerprint image. In particular, one could calculate the total number of xe2x80x9conxe2x80x9d-pixels above a given threshold and use this calculated value as an indicator of the force applied by the finger. Thus a third degree of freedom may be calculated. This third parameter could be used to control the third axis in a three-dimensional graphical user interface or application, or could be used to control an independent variable, such as a scroll bar, sound intensity, etc. Other information that may be calculated as control variables include the second moment of area, the orientation of the principal axis of the fingerprint, and the relative lengths of the major and minor axes.
With more sophisticated algorithms, related to those used for image pattern recognition, it is also possible to work out which part of a finger is in contact with the scanner. This information can also be used for control, most simply as two directions of rotation. It can thus be seen that using the absolute position, force, rotation in the plane of the scanner, and rolling the finger to bring different parts of the skin into contact with the scanner, that six degrees of freedom can be generated, which intuitively correspond to the six degrees of freedom of a rigid body in three-dimensional space. This provides a very natural method of interaction with a three dimensional simulation, such as a virtual world.